The disclosure relates to photosensitive glass. More particularly, the disclosure relates to photosensitive glasses that can be treated to form glass ceramics. Even more particularly, the disclosure relates to photosensitive lithium zinc aluminosilicate glasses and glass ceramics that may include both transparent and opaque or translucent (i.e., opalized) regions.
Glass-ceramics are nominally produced by a thermal process in which the as-made glass is thermally treated to produce a controlled crystalline phase. Cerium and silver photosensitizers have been used in glass systems, such as FOTOFORM™ and FOTA-LITE™, to produce photosensitive materials in which the crystal content is well below the 50% level that typically defines a glass ceramic. In such glass systems, an opal (i.e., opaque, optically dense, white, light scattering) phase containing NaF is formed in regions of the glass that are exposed to short wavelength light followed by heat treatment, while unexposed regions of the glass remain clear.